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to come to rest; a ball rolled on the ground,
a boat moved on the water, a shot fired in
the air. Galileo realised that in all of these
cases a resisting force acts to stop the mo-
tion, and he was the first to arrive at the
not very obvious law that the motion of a
body will never stop, nor vary its speed, nor
change its direction, except by the action of
some force.
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